The operator of a virtual (or real) camera frequently wishes to perform camera motions which end with a smooth transition to a stationary state. Virtual camera motions which involve smooth transitions to a stationary state are frequently desired in part because camera operators and audiences are accustomed to the motion of physical cameras whose motion is governed by inertial properties.
Typically, in control systems in which the speed of the camera motion is controlled by an input device such as a joystick, dynamic range issues prevent or significantly complicate the task of creating a smooth transition to a stationary state, particularly if the transition or “ease out” is to occur over a period of several seconds.
While it is possible to adjust the sensitivity curve of the controls (as discussed, for example, in U.S. patent application Ser. No. 11/261,441, already incorporated by reference) in order to expand the low-velocity region of the of the control system without sacrificing dynamic range and high velocity control, doing so generally results in a control system which is less satisfactory for general usage due to the changed sensitivity profile of the device. In particular, the sensitivity changes can raise the difficulty of causing the camera to start moving—from a still position—in a desired manner.
A common technique for smoothing the motion of real and virtual objects is to incorporate an inertial simulation into the control system. Such an inertial simulation is effectively a filter (e.g., a band pass filter) on the velocity of the device under control. Inertial solutions provide desirable motion but introduce a delay, or phase lag, into the control system, which is undesirable and which complicates the operator's task. The introduction of an inertial system frequently also complicates the operator's task on those occasions when a rapid transition from moving to stationary is desired (as useful as smooth transitions are, they are only one component of the storytelling grammar of the camera).
Thus, there are three complexities associated with this “ease out” problem. First, the problem is largely asymmetrical because it is far more common for a camera operator to want a slow transition to a stop than to want a slow transition to moving from a stop. Second, introducing delay or phase lag into the system is not generally desirable. Third, the mathematical properties of the desired transition differ from use to use.
There is a need for control systems that provide more robust tools for operating cameras, including without limitation, tools that address the ease out problem.